The use of abrasive washing techniques to achieve a desired "aging" of fabrics has long been known. The oldest and most widely used washing technique has been to add a certain amount of pumice stone to a washing machine and to wash the fabric in the presence of the pumice. However, this procedure has many drawbacks.
The pumice has a tendency to be ground to fine grit and break apart during use. The grit is very abrasive and serves to shorten the working life of moving washing machine parts. Furthermore, the clothes must be cleaned and processed to remove the grit after the abrasive process has been completed.
Also, as the stones break, the pieces are not of a uniform same size and often have shard edges or points. The non-uniform size of the stones leads to unpredictable fading of the fabric which can result in undesirable streaks or patterns in the fabric. The sharp edges or corners can also lead to the tearing or cutting of the fabric, making such damaged pieces unmerchantable.
Finally, the pumice stone has a relatively short life span and must be replaced frequently. Typically, pumice stone will only last for 2-3 wash cycles.
There have been many procedures developed to replace the requirement for pumice stones in a stone washing process. The various procedures take two basic approaches to the problem: chemical wash processes with no abrasive elements and/or replacement of pumice stone with a substitute abrasive number. The chemical procedures generally achieve good uniformity in the fading of the fabrics. However, the chemical processes have to date been unable to achieve the desired fabric texture, and the fading caused by the chemical processes does not quite duplicate the appearance of that achieved by pumice stones.
There have been attempts to develop abrasive members which provide some of the sought after improvements. Some processes have utilized a grit added to the wash which enhances uniformity and texture, but retains all of the problems of the Grit which is associated with pumice stones.
Another approach has been to manufacture artificial abrasive members or stones. German Patent No. 3,129,669, issued to Maruo Clothing, Inc., described the use of pieces of metal or hard plastic in place of stone. However, the surface of hard plastic is generally smooth and therefore lacks sufficient abrasive characteristics.
Another type of abrasive member was disclosed in U.S. Pat. No. 4,750,227 issued to Hopkins, et al. The abrasive member taught by Hopkins is a rigid block of material made of organic fibers covered by a resilient abrasive layer which is adhered to the rigid block. One problem with this product is that the outer or abrasive layer is subject to wear and the inner rigid block has different abrasive characteristics from the outer resilient layer. Therefore, this abrasive member is still subject to a shortened life span to avoid uneven abrasion of fabrics as the member wears.
It is therefore an object of the invention of a preferred embodiment to achieve the desired abrasion effects of pumice stone while providing uniformity of abrasion and wear and an extended operational life.
It is a further object of the invention to provide an artificial abrasive pellet which becomes pliable at wash water temperatures to enhance abrasion of fabrics.
It is a further object of the invention to provide an abrasive pellet which can be produced in a variety of shapes and sizes in order to achieve the desired abrasion affects.
It is a further object of this invention to provide an abrasive member of uniform composition throughout so that the abrasive characters remain uniform as it wears, thus extending its useful life.